The present invention relates to heating, ventilating, or air conditioning (HVAC) systems, and is directed more particularly to a portable control module that may be detachably connected in testing and control relationship to at least one of the subsystems of an HVAC system.
A commercial HVAC system typically includes a number of component systems or subsystems, such as chillers, which are constructed as discrete modular units, but which are controlled in such a way that they operate as cooperating portions of the system as a whole. The desired cooperation is usually achieved by connecting the subsystems together via a local equipment network or LEN. The system as a whole may then be monitored and controlled, from a central location, by using the LEN to receive operational and status information from the subsystems, and to send command and control information thereto.
In order to facilitate the troubleshooting and repair of the subsystems connected to a LEN, the subsystems are provided with local control units, which are often referred to as service modules or service ports. These service modules have control panels which include manually operable keys and displays that enable a service person to assume and exercise local control over the associated subsystems. The manually operable keys and displays may, for example, enable the service person to examine and/or change the setpoints of operating variables, such as pressure or temperature, to determine and/or change the currently selected operating mode or alarm settings, to initiate test sequences, etc. Because subsystems are often located at places where they exposed to the open air, the service modules thereof are usually provided with weatherproof housings that are securely attached to some part of the subsystem.
Because a subsystem, such as a chiller, is often much larger than the human being which services it, the service module thereof is preferably mounted on a part of the subsystem that is selected to enable the service person to observe the operation of as many of the moving parts thereof as is physically possible. Unfortunately, even the most carefully selected mounting location may be one that prevents the service person from seeing the operation of the very part that he wants to test. The service person was then faced with the problem of choosing between being able to initiate a test without being able to see the part to be tested, and being able to see the part to be tested without being able to initiate the test.
Prior to the present invention, the above-described problem was dealt with in one of two ways. One of these was to provide the service person with a second service person or helper, and to divide the task of servicing the subsystem between the two. This solved the problem, but significantly reduced the productivity of the servicing process. It also created a risk that mistakes or misunderstandings on the part of one of the service persons might result in injury to the other.
Another way of solving the problem was to provide each subsystem with a multiplicity of alternately usable service modules. This too solved the problem, but significantly increased the cost and complexity of each subsystem. It also decreased the reliability of the system as a whole by increasing the number of ways in which its subsystems could fail.
In view of the foregoing, it will be seen that, prior to the present invention, there has existed a need for an apparatus which could be used to facilitate the performance of the test and control functions of the service module of an HVAC system, and which could be used without decreasing either the productivity of those who service that system, or the reliability of the system as a whole.